Optical scanner

ABSTRACT

An optical scanner includes a frame, a light source, an optical member, and a spacer. The light source emits a light beam. The optical member is mounted on the frame to guide the light beam to a scanning target. The spacer maintains the optical member at a predetermined position with respect to the frame. The spacer is formed of a photocurable resin that is cured in response to a predetermined light having a wavelength within a prescribed range.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical scanner that scans a lightbeam, and particularly to an optical scanner employed in the scanningdevice of an electrophotographic image-forming device.

2. Description of Related Art

Electrophotographic image-forming devices, such as laser printers,employ an optical scanner (scanning device) to emit a beam of light ontoa photosensitive drum, enabling the exposed regions of the drum to carrya toner image. The toner image carried on the photosensitive drum issubsequently transferred onto a recording medium, such as paper or atransparency, forming an image thereon.

The optical scanner is configured of a light source, and opticalmembers, such as mirrors and lenses, for deflecting the light emittedfrom the light source and for guiding the light toward thephotosensitive drum.

If the mounted angles of the optical members are inexact, the light willnot be irradiated onto the photosensitive drum parallel to the axis ofthe photosensitive drum but will be slanted or curved, making itimpossible to guide the light beam to prescribed positions on thephotosensitive drum. Consequently, the quality of the images formed on arecording medium will degrade.

Therefore, technologies such as that disclosed in Japanese unexaminedpatent application publication No. 2001-215434 have been proposed foradjusting the mounted angles of the mirrors. An angle regulating screwwith a tip contacting the mirror is rotated to adjust the protrudinglength of the screw, thereby adjusting the mounted angle of the mirror.The regulating screw also maintains the mirror at this mounted angle.

However, due to manufacturing irregularities within the range oftolerance, play similar to the backlash in a gear mechanism is producedbetween the external threaded part of the screw (male screw) and theinternal threaded part (female screw) through which the male screw isinserted. Hence, even after adjusting the mounted angle of the mirrorswith the technology disclosed in Japanese unexamined patent applicationpublication No. 2001-215434, the angle regulating screw cannot maintainthe adjusted angle due to the play produced between the male screw andthe female screw.

Although this problem of play produced between the male and femalescrews can be reduced by increasing the manufacturing precision in thescrew parts, such an increase in manufacturing precision leads to a risein costs for manufacturing the angle regulating screw.

Further, while in theory the protruding length of the regulating screwchanges continuously in proportion to the rotational amount of thescrew, in reality this does not occur due to the play between the screwparts. In other words, the protruding length of the regulating screwvaries discontinuously relative to the rotational amount of the screw.

Hence, since the invention in Japanese unexamined patent applicationpublication No. 2001-215434 cannot maintain the mirrors at a desiredmounted angle, this technology cannot maintain optical members, such asmirrors and lenses, at suitable mounted angles.

Further, if the surface precision in the part of the regulating screwthat contacts the mirror or if the surface precision in the part of themirror that contacts the regulating screw is low, the optical memberscannot be maintained such that the mounted angle of the mirrors issuitable.

While this problem can be resolved by increasing the surface precisionin these contact areas, this resolution also leads to an increase inmanufacturing costs for the regulating screw and mirror.

Further, dust buildup on mirrors, lenses, or other optical members is aprimary cause of poor performance in the optical scanner. Poorperformance caused by such dust buildup can be resolved by removing theoptical members from the frame and cleaning the members.

However, the regulating screws must be loosened in order to remove themirrors or other optical members in the invention disclosed in Japaneseunexamined patent application publication No. 2001-215434. When theoptical member that was removed and cleaned is subsequently remounted onthe frame, the mounted angle of the optical member must be readjusted,even when the member is being mounted on the same frame. Accordingly,the invention disclosed in Japanese unexamined patent applicationpublication No. 2001-215434 is not suited for reassembling the opticalscanner. That is, maintenance of the optical scanner is not facilitatedwith this technology.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide an optical scanner that is easier to maintain (easier toreassemble) and that can easily maintain optical members at a suitablemounted angle.

In order to attain the above and other objects, the present inventionprovides an optical scanner including a frame, a light source, anoptical member, and a spacer. The light source emits a light beam. Theoptical member is mounted on the frame to guide the light beam to ascanning target. The spacer maintains the optical member at apredetermined position with respect to the frame. The spacer is formedof a photocurable resin that is cured in response to a predeterminedlight having a wavelength within a prescribed range.

Another aspect of the present invention provides an image-forming deviceincluding a plurality of image-carrying members and an optical scanner.A plurality of laser beam is scanned on the plurality of image-carryingmembers, respectively, to form a color image on a recording medium. Theoptical scanner includes a frame, a light source, a plurality of opticalmembers, and a spacer. The light source emits a plurality of lightbeams. The plurality of optical members is mounted on the frame to guidethe plurality of light beams to the plurality of image-carrying members.The spacer maintains the optical member at a predetermined position withrespect to the frame. The spacer is formed of a photocurable resin thatis cured in response to a predetermined light having a wavelength withina prescribed range. The number of the plurality of optical members is noless than number of the plurality of image-carrying members.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the inventionwill become more apparent from reading the following description of thepreferred embodiments taken in connection with the accompanying drawingsin which:

FIG. 1 is a side cross-sectional view of a laser printer according to apreferred embodiment of the present invention;

FIG. 2 is a plan view showing the overall structure of a scanning unitaccording to the preferred embodiment;

FIG. 3 is a side cross-sectional view showing the overall structure ofthe scanning unit;

FIG. 4 is an exploded perspective view showing the scanning unit andmain frame according to the preferred embodiment;

FIG. 5 is a bottom view of the scanning unit;

FIG. 6 is the same view in FIG. 5 when a cover member has been removedfrom the scanning unit;

FIG. 7 is a perspective view showing a portion of the scanning unit fromthe bottom;

FIG. 8 is a schematic cross-sectional view showing an exit hole coverand a cover clamp according to the preferred embodiment;

FIG. 9 is an enlarged view of a part B shown in FIG. 3;

FIG. 10A is an enlarged view of a part A shown in FIG. 2;

FIG. 10B is a cross-sectional view along a line XB-XB shown in FIG. 10A;

FIG. 10C is a cross-sectional view along a line XC-XC shown in FIG. 10A;

FIG. 11A is a cross-sectional view of a scanning unit having a structuredifferent from that in the preferred embodiment;

FIG. 11B is a cross-sectional view illustrating a feature of thescanning unit according to the preferred embodiment;

FIG. 12 is a perspective view showing a mirror mounted on the scannerframe according to the preferred embodiment;

FIG. 13 is an exploded cross-sectional view of the mirror and scanningframe in FIG. 12;

FIG. 14A is a view of the mirror and scanning frame from the viewpointindicated by an arrow C in FIG. 12;

FIG. 14B is a cross-sectional view along a line XIVB-XIVB shown in FIG.14A;

FIG. 15 is a cross-sectional view showing a laser printer according to asecond embodiment of the present invention;

FIG. 16 is a side cross-sectional view showing an operational feature ofthe laser printer according to the second embodiment;

FIG. 17A is a plan view showing a mirror mounted on the scanner frameaccording to a third embodiment of the present invention;

FIG. 17B is a cross-sectional view along a line XVIIB-XVIIB shown inFIG. 17A;

FIG. 18A is a plan view showing a mirror mounted on the scanner frameaccording to a fourth embodiment of the present invention; and

FIG. 18B is a cross-sectional view along a line XVIIIB-XVIIIB shown inFIG. 18A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An optical scanner according to preferred embodiments of the presentinvention will be described while referring to the accompanying drawingswherein like parts and components are designated by the same referencenumerals to avoid duplicating description.

In the following description, the expressions “front”, “rear”, “upper”,“lower”, “right”, and “left” are used to define the various parts whenthe optical scanner is disposed in an orientation in which it isintended to be used.

In the preferred embodiments, the optical scanner according to thepresent invention is applied to an electrophotographic color laserprinter. Next, the preferred embodiments will be described whilereferring to the accompanying drawings.

First Embodiment

FIG. 1 is a side cross-sectional view showing the primary components ofa laser printer 100. The laser printer 100 includes a substantiallybox-shaped (cubical) casing 103. A discharge tray 105 is provided on thetop surface of the casing 103 for receiving and holding a recordingmedium, such as paper or transparencies (hereafter simply referred to as“paper”), discharged from the casing 103 after a printing operation.

The casing 103 accommodates a feeding unit 300 for supplying paper to beprinted, a conveying mechanism 350 for conveying paper fed from thefeeding unit 300, and an image-forming unit 200 for forming images onthe paper. The image-forming unit 200 includes four process cartridges500K, 500Y, 500M, and 500C.

After the image-forming unit 200 has formed an image on the paper, anintermediate conveying roller 380 and a discharge chute (not shown)convey the paper upward in a paper-conveying direction that changesabout 180 degrees. Subsequently, a discharge roller 390 discharges thepaper through a discharge opening 107 onto the discharge tray 105.

The feeding unit 300 includes a paper tray 301 accommodated in thelowermost section of the casing 103, a feeding roller 303 for feeding(conveying) paper stacked in the paper tray 301 to the image-formingunit 200, and a separating pad 305 for separating the sheets of paper sothat the paper is fed by the feeding roller 303 one sheet at a time.

Paper fed from the paper tray 301 is conveyed along a U-shaped path inthe front side of the casing 103 so as to be conveyed toward theimage-forming unit 200 disposed substantially in the center of thecasing 103. Provided along this paper-conveying path from the paper tray301 to the image-forming unit 200 are a conveying roller 307, a pinchroller 309 for pressing the paper against the conveying roller 307, aregistration roller 311 disposed farther downstream from the conveyingroller 307 in the paper-conveying direction, and a registration roller313 disposed in opposition to the registration roller 311.

The conveying mechanism 350 is configured of a drive roller 351, afollow roller 353, and a conveying belt 355 looped around the driveroller 351 and follow roller 353. When the drive roller 351 rotates sothat the top side of the conveying belt 355 moves in the paper-conveyingdirection, a sheet of paper fed from the paper tray 301 onto theconveying belt 355 is conveyed sequentially to each of the four processcartridges 500K, 500Y, 500M, and 500C in a direction toward the rear ofthe laser printer 100.

In the preferred embodiment, a belt cleaner 360 is disposed on thebottom side of the conveying mechanism 350 for removing waste tonerdeposited on the surface of the conveying belt 355.

The image-forming unit 200 includes a scanning unit 400, the fourprocess cartridges 500K, 500Y, 500M, and 500C, a fixing unit 600, andfour transfer rollers 570 corresponding to the four process cartridges500K, 500Y, 500M, and 500C.

The image-forming unit 200 according to the preferred embodiment is adirect tandem type system capable of printing color images. In thepreferred embodiment, the four process cartridges 500K, 500Y, 500M, and500C correspond to the toner colors black (K), yellow (Y), magenta (M),and cyan (C) and are arranged in a series along the paper-conveyingdirection from the upstream side to the downstream side in the ordergiven above. The process cartridges 500K, 500Y, 500M, and 500C have thesame configuration, differing only in the color of toner used.Therefore, the process cartridges 500K, 500Y, 500M, and 500C will bereferred to collectively as “process cartridges 500” below. Each of theprocess cartridges 500 is provided with a corresponding photosensitivedrum 510 (i.e., photosensitive drums 510K, 510Y, 510M, and 510C).

The scanning unit 400 functions to irradiate laser beams onto thephotosensitive drums 510, forming an electrostatic latent image on thesurfaces of the photosensitive drums 510 exposed to the laser beam. Inthe preferred embodiment, the scanning unit 400 employs the opticalscanner according to the present invention.

As shown in FIG. 1, the scanning unit 400 is disposed in the uppersection of the casing 103 above the process cartridges 500. Laser beamsare irradiated toward the photosensitive drums 510 through the bottomsurface of the scanning unit 400. The scanning unit 400 will bedescribed in greater detail later.

As shown in FIG. 1, the process cartridge 500 is detachably mounted inthe casing 103 below the scanning unit 400. The process cartridge 500includes the photosensitive drum 510, a charger 520, a toneraccommodating section 530, and the like accommodated in a casing 560.

The transfer roller 570 is rotatably supported in a main frame 110 (seeFIG. 4) at a position opposing the photosensitive drum 510 with theconveying belt 355 interposed therebetween. In the preferred embodiment,the four process cartridges 500 are accommodated in a single casing 560so that the four process cartridges 500 can be integrally mounted in themain frame 110.

The photosensitive drum 510 functions to carry an image to betransferred onto the paper. The charger 520 functions to charge thesurface of the photosensitive drum 510. The transfer roller 570functions to transfer toner carried on the surface of the photosensitivedrum 510 to the printing surface of the paper.

The toner accommodating section 530 is configured of a toner chamber 531for accommodating toner, a supply roller 532 for supplying toner ontothe photosensitive drum 510, a developing roller 533, and the like. Thetoner accommodating section 530 according to the preferred embodiment isdetachably mounted in the casing 560.

The supply roller 532 rotates to supply toner accommodated in the tonerchamber 531 toward the developing roller 533. Toner supplied toward thedeveloping roller 533 is carried on the surface thereof, while athickness-regulating blade 534 regulates the thickness of toner carriedon the surface of the developing roller 533 to maintain a uniformthickness. Subsequently, the developing roller 533 supplies the uniformlayer of toner onto the surface of the photosensitive drum 510 exposedby the scanning unit 400.

The fixing unit 600 uses heat to melt the toner transferred onto thepaper for fixing the toner to the paper. The fixing unit 600 isdetachably mounted in the main frame 110. The fixing unit 600 includes aheating roller 610, a pressure roller 620, and the like.

The image-forming unit 200 forms images on paper as follows.Specifically, the charger 520 provides a uniform charge on the surfaceof the photosensitive drum 510 as the photosensitive drum 510 rotates.Subsequently, the scanning unit 400 irradiates a laser beam onto thephotosensitive drum 510, exposing the surface of the photosensitive drum510 with a high-speed scan. In this way, the scanning unit 400 forms anelectrostatic latent image on the surface of the photosensitive drum 510corresponding to an image to be formed on the paper.

Next, as the developing roller 533 rotates, the positively charged tonercarried on the surface of the developing roller 533 is selectivelysupplied onto the surface of the photosensitive drum 510 when the tonercomes into contact therewith. The supplied toner develops theelectrostatic latent image on the photosensitive drum 510 into a visibleimage so that a toner image produced according to reverse development iscarried on the surface of the photosensitive drum 510.

Subsequently, a transfer bias applied by the transfer roller 570 causesthe toner image carried on the surface of the photosensitive drum 510 totransfer onto the paper. Next, the paper is conveyed to the fixing unit600, where the toner image newly transferred onto the paper is heatedand fixed to the paper, thereby completing image formation.

Next, the scanning unit 400 according to the preferred embodiment willbe described in detail with reference to FIGS. 2-14B.

FIG. 2 is a plan view showing the general structure of the scanning unit400. For the sake of description, corners 431G described later have beenomitted from FIG. 2. FIG. 3 is a side cross-sectional view showing theoverall structure of the scanning unit 400. As shown in FIG. 2, thescanning unit 400 has four light sources 403K, 403Y, 403M, 403C(hereinafter collectively referred to as “light sources 403”).

The light sources 403K, 403Y, 403M, 403C irradiate light onto therespective photosensitive drums 510K, 510Y, 510M, and 510C shown in FIG.3. Each of the light sources 403K, 403Y, 403M, 403C has a respectivesemiconductor laser 401K, 401Y, 401M, and 401C (hereinafter collectivelyreferred to as “semiconductor lasers 401”) for emitting a laser light,and a respective collimator lens 402K, 402Y, 402M, and 402C (hereinaftercollectively referred to as “collimator lenses 402”). Each collimatorlens 402 is provided on the front surface of the respectivesemiconductor laser 401 for converting divergent rays emitted from thesemiconductor laser 401 into parallel rays forming a beam.

A mirror 404C deflects light emitted from the light source 403Capproximately 90 degrees toward a cylindrical lens 405A. A mirror 404Mdeflects light emitted from the light source 403M approximately 90degrees toward a cylindrical lens 405B.

Light guiding parts (not shown) are provided in regions shifted towardthe far side in the drawing relative to the mirror 404C and mirror 404M,respectively, for guiding light emitted from the light source 403K tothe cylindrical lens 405A and light emitted from the light source 403Yto the cylindrical lens 405B.

As shown in FIG. 3, Light from the light sources 403C and 403K guided tothe cylindrical lens 405A is refracted by the cylindrical lens 405A andirradiated onto reflecting surfaces of a polygon mirror 406 at differentangles of incidence. Similarly, light from the light sources 403Y and403M guided to the cylindrical lens 405B is refracted by the cylindricallens 405B and irradiated onto reflecting surfaces of the polygon mirror406 at differing angles of incidence.

The polygon mirror 406 is configured of a rotating multifaceted mirrorconfigured of reflecting mirrors arranged in a polygonal (hexagonal inthe preferred embodiment) shape. The polygon mirror 406 functions todeflect and scan light emitted from the light sources 403 when rotatedby an electric motor (not shown). The laser beam is scanned in theleft-to-right direction of FIG. 2 at a constant angular velocity.

fθ lenses 407A and 407B (hereinafter collectively referred to as “fθlenses 407”) function to convert the constant angular velocity in whichthe polygon mirror 406 scans the laser beam in the left-to-rightdirection of FIG. 2 into a constant linear velocity in which the laserbeam is scanned over the photosensitive drum 510.

As shown in FIG. 3, optical members configured of a plurality of mirrors410-419, toric lenses 420K, 420Y, 420M, and 420C (hereinaftercollectively referred to as “toric lenses 420”), and the like focus thelaser beams onto the photosensitive drums 510 after the fθ lenses 407have converted the scanning velocity of the beams.

The toric lenses 420 are lenses that have different curvatures in themain scanning direction and subscanning direction of the laser beam. Thetoric lenses 420 functions to correct face tangle error by deflecting inthe subscanning direction light reflected by the polygon mirror 406 in adirection different from the regulated direction.

With this construction, as shown in FIGS. 3 and 4, light emitted fromthe light sources 403 based on image data passes through the cylindricallenses 405A and 405B (hereinafter collectively referred to as the“cylindrical lenses 405”) and is deflected and scanned by the polygonmirror 406, while the scanning speed is converted to a constant linearvelocity by the fθ lenses 407. Subsequently, the mirrors 410-419 bendthe optical axis of the light beams so that the beams are irradiated onthe photosensitive drums 510 via the toric lenses 420, forming imagesthereon.

Of the mirrors 410-419, the mirror 410 does not reflect all light.Specifically, the mirror 410 reflects light emitted from the lightsource 403C toward the mirror 411, but refracts and passes light emittedfrom the light source 403K toward the mirror 413.

However, if dust particles become deposited on the surfaces of themirrors or lenses, i.e., the polygon mirror 406, mirrors 410-419, fθlenses 407, and toric lenses 420, the scanning unit 400 may lose itsability to form clear electrostatic latent images on the photosensitivedrums 510.

Therefore, the mirrors and lenses are accommodated in a casing 430 inthe preferred embodiment, as shown in FIG. 3, protecting the mirrors410-419, fθ lenses 407, and toric lenses 420 from dust. The casing 430is configured of a scanner frame 431 for mounting and fixing the mirrors410-419, toric lenses 420, and the like; a cover member 432 for coveringthe underside (process cartridges 500 side) of the scanner frame 431;and a scanner cover 433 for covering the top side (opposite side fromthe process cartridges 500) of the scanner frame 431. The scanner cover433 is formed of a synthetic resin or metal.

FIG. 4 is an exploded perspective view showing the scanning unit 400 andthe main frame 110. FIG. 5 shows a bottom view of the scanning unit 400.FIG. 6 shows a section of the scanning unit 400 in FIG. 8 when the covermember 432, exit hole covers 436, and cover clamps 440 have been removedfrom the scanning unit 400.

The scanner frame 431 is formed of a PC/ABS polymer alloy throughinjection molding and is filled with filler having isotropic thermalexpansion properties. Protrusions 434 (boss parts) are formed on thebottom surface of the scanner frame 431 on both left and right sidesthereof. The protrusions 434 function to position and fix the scanningunit 400 on the main frame 110 of the laser printer 100. The protrusions434 are disposed along a straight line in the left-to-right directionthat passes substantially through the center of the polygon mirror 406and are positioned substantially in the front-to-rear center of thescanner frame 431.

Four corners 431G of the scanner frame 431 are pressed against the mainframe 110 (see FIG. 4) by elastically deformable pressing members (notshown), such as U-shaped leaf spring clips. Since the four corners 431Gis not fixed on the main frame 110, this construction allows thelongitudinal ends of the scanner frame 431 to be slidingly displacedrelative to the main frame 110, while the positions of the protrusions434 relative to the main frame 110 remain unchanged.

Even when the thermal expansion of the scanner frame 431 differs greatlyfrom that of the metal main frame 110, a great thermal stress will notbe generated in the scanner frame 431 since the longitudinal ends of thescanner frame 431, are displaced relative to the main frame 110. Hence,it is possible to suppress deformation in the scanner frame 431 due tothermal stress, while preventing the center positions of the scannerframe 431 from changing relative to the main frame 110.

By reducing the amount of deviation in the focus position at which lightemitted from the scanning unit 400 strikes the photosensitive drum 510,this construction can prevent problems in color registration caused bysuch deviations.

As shown in FIG. 3, the cover member 432 includes a first cover member432A covering the region of the scanner frame 431 spanning from thefront-to-rear center to the front side, and a second cover member 432Bfor covering the region spanning from the front-to-rear center to therear side. The first and second cover members 432A and 432B are metalplate parts molded by pressing metal plates formed of SPCC (cold rolledsteel).

Two exit holes 435K and 435C are formed in the first cover member 432Ato allow the passage of light emitted toward the photosensitive drums510K and 510C. Two exit holes 435M and 435Y are formed in the secondcover member 432B to allow the passage of light emitted toward thephotosensitive drums 510M and 510Y. Hereafter, the first and secondcover members 432A and 432B will be collectively referred to as “covermembers 432,” while the four exit holes 435K, 435C, 435M, and 435Y willbe collectively referred to as “exit holes 435.”

By forming a plurality of the exit holes 435 in a single cover member432, rather than providing a cover member 432 for each of the exit holes435, the number of cover members 432 can be reduced, reducing theoverall number of parts in the scanning unit 400.

The exit holes 435 are sealed by exit hole covers 436K, 436C, 436M, and436Y (hereinafter collectively referred to as “exit hole covers 436”)configured of a light transmissible material (glass or transparentacrylic in the preferred embodiment). The exit hole covers 436 areprovided on the outer side of the casing 430 (see FIG. 9). In otherwords, a bottom surface 436A of the exit hole cover 436 is positionedlower than an outer surface 432A of the casing 430 (the cover member432). As shown in FIG. 3, all bottom surfaces 436A are positioned insubstantially the same plane.

By positioning the bottom surfaces 436A of the exit hole covers 436lower than the outer surface 430A of the casing 430 in this way, theexit hole covers 436 are easier to clean than when the bottom surfaces436A of the exit hole covers 436 are positioned inside (higher than) theouter surface 430A of the casing 430, thereby maintaining the quality ofimages formed on paper for a longer period of time.

Further, since the bottom surfaces 436A of the exit hole covers 436 arepositioned substantially in the same plane, the plurality of exit holecovers 436 can be easily cleaned at the same time.

As shown in FIG. 9, a portion of the toric lenses 420 is positionedinside the exit holes 435, the toric lenses 420 being the opticalmembers positioned last in the optical path among the optical members(i.e., the mirrors 410-419, the fθ lenses 407, and the toric lenses 420)for focusing light emitted from the light sources 403 on thephotosensitive drums 510.

In other words, in the preferred embodiment, the toric lenses 420 arefixed in the casing 430 so that ends of the toric lenses 420 positionedon the exit hole cover 436 side are positioned closer to the exit holecovers 436 than a surface 430B on the inside of the cover members 432around the exit holes 435.

Positioning at least part of the toric lenses 420 inside the exit holes435 reduces the distance between the scanning unit 400 and thephotosensitive drums 510, thereby reducing the distance between thetoric lenses 420 and the photosensitive drums 510. By reducing thedistance between the toric lenses 420 and photosensitive drums 510, itis possible to reduce the image magnification, thereby preventing theeffects of deviations in the light sources 403 and the like from beingamplified and, hence, preventing large deviations in the positions atwhich the light strikes the photosensitive drums 510. Accordingly, thisconstruction improves the quality of images formed on the paper, whileincreasing the distance between the exit hole covers 436 and thephotosensitive drums 510, enabling the space between the exit holecovers 436 and photosensitive drums 510 to be used effectively.

FIG. 7 is a perspective view showing a portion of the scanning unit 400from the bottom. As shown in FIG. 7, the exit hole covers 436 are formedin strips extending in the main scanning direction (left-to-rightdirection in the preferred embodiment) of the laser beams. As shown inFIG. 9, the exit hole covers 436 are fitted into recessed parts 432Dformed in the peripheral edge portion of the exit holes 435 forpositioning the exit hole covers 436 relative to the cover members 432.The cover clamps 440 (FIG. 5) press the longitudinal ends of the exithole covers 436 against the cover members 432, fixing the exit holecovers 436 on the cover members 432.

FIG. 8 is a schematic cross-sectional view showing the exit hole cover436 and the cover clamp 440. As shown in FIG. 8, the cover clamp 440 issubstantially L-shaped and configured of a first plate part 441 coveringan end part of the exit hole cover 436, and a second plate part 442extending in a direction orthogonal to the first plate part 441. Anengaging hole 442A is formed in the second plate part 442, and anengaging protrusion 431A is formed on the scanner frame 431 for fittinginto the engaging hole 442A. By engaging the engaging protrusions 431Ain the engaging holes 442A, the cover clamps 440 are fixed to thescanner frame 431.

The cover clamp 440 is configured of an L-shaped leaf spring. Beforemounting the cover clamp 440 on the casing 430, the angle formed by thefirst and second plate parts 441 and 442 is slightly less than 90degrees.

Therefore, when the cover clamp 440 is mounted on the casing 430 byfitting the engaging protrusion 431A in the engaging hole 442A, thecover clamp 440 deforms elastically so that the first and second plateparts 441 and 442 form an angle of 90 degrees. Accordingly, when theexit hole cover 436 is fixed to the casing 430, the elastic force(restoring force) generated by the cover clamp 440 presses against thecover member 432.

An engaging hole 432C is also formed in the cover member 432 forengaging with the engaging protrusion 431A (i.e., the engagingprotrusion 431A is fitted into the engaging hole 432C. Hence, the covermember 432 is positioned relative to the scanner frame 431 by engagingthe engaging protrusion 431A and engaging hole 432C. When the engagingprotrusion 431A is engaged in the engaging hole 432C, the cover clamp440 presses the cover member 432 against the exit hole cover 436 and thescanner frame 431, thereby fixing the cover member 432 and exit holecover 436 on the scanner frame 431 with pressure.

Constructing the cover clamps 440 to press the exit hole cover 436against the casing 430 on both ends of the exit hole cover 436 in themain scanning direction not only prevents the cover clamps 440 fromobstructing the optical path of the laser beam during a scanningoperation, but also prevents the cover clamps 440 from interfering withcleaning of the exit hole cover 436. Hence, this constructionfacilitates cleaning of the exit hole covers 436.

Further, since the cover clamps 440 are substantially L-shaped with thesection on the process cartridge 500 side formed as a flat surface withno protrusions, the cover clamps 440 do not protrude toward the processcartridge 500 side. Therefore, the size of the process cartridge 500(toner accommodating section 530 can be increased to increase tonercapacity, without interference between the process cartridge 500 and thecover clamps 440. The cover clamps 440 also do not interfere whenmounting the process cartridge 500.

As shown in FIG. 8, lens clamps 445 are provided for pressing and fixingthe toric lens 420 against the scanner frame 431. As with the coverclamp 440, the lens clamp 445 is configured of an L-shaped leaf springmember.

More specifically, an engaging hole 445A is formed in the lens clamp445, and a spring part 445B is formed on the lens clamp 445. Theengaging hole 445A fits over (engages with) an engaging protrusion 431Dformed on the scanner frame 431 and fits into a recessed part 431Eformed in the scanner frame 431. At this time, the spring part 445Bgenerates an elastic force for pressing the lens clamp 445 toward thebase of the engaging protrusion 431D.

Hence, the lens clamp 445 is positioned relative to the scanner frame431 when the engaging protrusion 431D is fitted into the engaging hole445A and is firmly fixed relative to the scanner frame 431 by theelastic force (pressing force) generated by the spring part 445B. At thesame time, the lens clamp 445 presses the toric lens 420 against thescanner frame 431 so that the toric lens 420 contacts a region 431H ofthe scanner frame 431, thereby fixing the position of the toric lens 420in the thickness direction (vertical direction) of the scanner frame431.

As shown in FIG. 5, an electric harness 406A is arranged in an area ofthe casing 430 corresponding to a region in which the cover member 432is provided. The electric harness 406A supplies a drive current andcontrol signals for controlling an electric motor that rotates thepolygon mirror 406. Accordingly, the metal cover member 432 shields amagnetic field induced by current flowing through the electric harness406A, preventing the magnetic field from leaking outside of the casing430.

By forming the cover member 432 of metal rather than a synthetic resin,the walls of the cover member 432 can be made thinner while maintainingthe same stiffness as that of a cover member 432 formed of resin. Hence,this construction does not contribute to an increased size of the laserprinter 100 and can maintain a prescribed gap between the scanning unit400 and process cartridges 500.

Further, forming the cover member 432 of press-molded metal plate partsimproves the productivity for the cover member 432 and reduces the basemanufacturing costs of the scanning unit 400.

FIG. 10A is an enlarged view of parts A shown in FIG. 2. FIG. 10B is across-sectional view along a line XB-XB in FIG. 10A. FIG. 10C is across-sectional view along a line XC-XC in FIG. 10A. As shown in FIG.10A, wall parts 413G connected to the scanner frame 431 are providedbetween the fθ lens 407 and polygon mirror 406 (FIG. 2) for fixing thefθ lens 407 to the scanner frame 431. The fθ lens 407 is fixed to thewall parts 413G by both ends in the main scanning direction of the laserbeam.

In the preferred embodiment, clips 407C forming three sides of arectangle in cross section are elastically deformed to fit over the fθlens 407 and wall part 413G, thus fixing the fθ lens 407 to the wallpart 413G.

As shown in FIG. 10A, a bridge part 413K bridges the two clips 407C. Asshown in FIG. 10B, an optical path opening 413H is formed between thescanner frame 431 and the bridge part 413 k. As shown in FIGS. 3 and 10Ato 10C, a through-hole 413L is formed in the scanner frame 431 at anopposing position to the bridge part 413K for constructing an opticalpath leading to the exit hole 435.

In the preferred embodiment, the wall part 413G, bridge part 413K, andscanner frame 431 are integrally formed by a molding process.

Thus, the bridge part 413K provided between the wall parts 413Gincreases the bending stiffness of the scanner frame 431, which includesthe wall part 413G for fixing the fθ lens 407. Therefore, thisconstruction prevents a decrease in stiffness of the scanner frame 431when the through-hole 413L is formed on the side of the optical pathopening 413H opposite the bridge part 413K.

Normally, the mirrors, including the polygon mirror and mirrors, and thelenses, including the toric lenses, are accommodated in the casing forprotection from dust particles. However, since the laser printerdeflects and scans light beams emitted from the light sources byrotating the polygon mirror, regardless of whether the laser printer isa color or monochrome printer, the rotating motion of the polygon mirroragitates air in the casing, producing airflow. Consequently, air outsidethe casing is drawn into the casing through gaps between the exit holecover and casing.

Of the gaps between the exit hole cover and casing in fluidcommunication with the region outside the casing, some gaps are toosmall to allow the passage of dust particles. These gaps act as a filterand trap and accumulate dust particles therein.

At this time, if the exit hole cover 436 is disposed on the inside ofthe casing 430 with the exit hole 435 exposed on the outside of thecasing, as shown in FIG. 11A, dust particles that cannot pass throughgaps between the exit hole cover 436 and the casing 430 accumulate inedges of the exit hole 435, obstructing the same.

However, since the exit hole cover 436 is provided in the outside of thecasing 430 in the preferred embodiment, the exit hole 435 is not exposedto the outside of the casing 430, but is entirely covered by the exithole cover 436.

Therefore, as illustrated in FIG. 11B, dust particles that cannot passthrough gaps between the exit hole cover 436 and the casing 430accumulate at outer edge regions of the exit hole cover 436 rather thanin edges of the exit hole 435. Therefore, the structure according to thepreferred embodiment prevents the accumulation of dust particles thatare unable to pass through gaps between the exit hole cover 436 and thecasing 430 from obscuring the exit hole 435, thereby reducing thefrequency of cleaning (maintenance frequency) required for the exit holecover 436 and improving user-friendliness of the laser printer 100.

When manufacturing the casing 430 by an injection molding method orother molding process, restrictions in the manufacturing process(related to removing the molded part) may require that an opening beformed in a region of the casing 430 opposing the photosensitive drum510. Since the casing 430 is configured of a main casing part (thescanner frame 431 and scanner cover 433) and the cover member 432 in thepreferred embodiment, the opening provided in the main casing part as arequirement of the manufacturing process can be sealed with the covermember 432, thereby reliably protecting the light sources 403, polygonmirror 406, mirrors 410-419, and the like from dust particles.

Next, the configuration for mounting and fixing the mirrors 410-419 tothe scanner frame 431 will be described, referring to FIGS. 12 to 14B.Light emitted from the light sources 403 follows optical paths that arebent by the mirrors 410-419 before the laser beam reaches the toriclenses 420. Accordingly, if the mounted angles of the mirrors 410-419relative to the scanner frame 431 are inexact, the laser beams will notbe suitably focused on the photosensitive drums 510.

Hence, even if the angles of the mirrors 410-419 are adjustedappropriately when assembled, if the mounted angles were later tochange, the light beams would not be focused appropriately on thephotosensitive drums 510 for forming images reliably on paper.Consequently, the quality of the images formed on the paper woulddecline.

This problem is resolved in the preferred embodiment by fixing themirrors 410-419 to the scanner frame 431 according to the followingconstruction. Since the construction for fixing the mirrors 410-419 tothe scanner frame 431 is the same for each mirror, the construction forassembling the mirror 411 will be used as an example of the assemblystructure in the preferred embodiment.

FIG. 12 is a perspective view showing the mirror 411 mounted on thescanner frame 431. FIG. 13 is an exploded cross-sectional view of themirror 411 and scanning frame 431 in FIG. 12. As shown in FIGS. 12 and13, the mirror 411 is formed of a glass plate extending as a strip inthe scanning direction of the laser beam. A reflecting surface(reflecting film) 411A for reflecting light is formed through vapordeposition of aluminum or another metal on a side surface of the glassplate on which light is incident. Metal is not deposited on thelongitudinal ends of the mirror 411 to which mirror clamps 470 describedlater are attached, allowing light to pass therethrough.

FIG. 14A is a view of the mirror 411 and scanning frame 431 from theviewpoint indicated by an arrow C in FIG. 12. FIG. 14B is across-sectional view along a line XIVB-XIVB shown in FIG. 14A. As shownin FIGS. 12 and 14B, the mirror clamps 470 fix the mirror 411 on thescanner frame 431, while pressing the mirror 411 toward the scannerframe 431. The mirror clamp 470 positions the mirror 411 relative to thescanner frame 431 on a seating member 450.

As shown in FIG. 14A, the seating member 450 is disposed between thescanner frame 431 and the mirror 411 on each longitudinal end thereof.As shown in FIG. 14B, the seating member 450 has a protruding supportpart 451, and a plate part 452 that are integrally formed of aluminum oranother metal. The protruding support part 451 serves as a reference foradjusting the mounted angle of the mirror 411. The protruding supportpart 451 protrudes from the mirror 411 side of the plate part 452 andcontacts the reflecting surface 411A of the mirror 411 with the distalend thereof.

As shown in FIG. 13, the protruding support part 451 is a protrusionextending in the longitudinal direction of the mirror 411. As shown inFIG. 14A, the region of contact between the protruding support part 451and reflecting surface 411A of the mirror 411 is an extension of ascanning path L1 of the laser beam.

As shown in FIG. 13, a groove 453 is formed in a bottom surface of theplate part 452 extending in a direction orthogonal to the longitudinaldirection of the mirror 411. By fitting a protruding part 431B formed onthe scanner frame 431 in the groove 453, the position of the seatingmember 450 is fixed in the longitudinal direction of the mirror 411.

Side parts 452A of the plate part 452 contact step parts 431C formed onthe protruding part 431B to position the seating member 450 in adirection orthogonal to the longitudinal direction of the mirror 411.

As shown in FIG. 14B, spacers 460 are provided between the mirror 411and plate part 452 on both sides of the protruding support part 451 formaintaining the mounted angle of the mirror 411 relative to the scannerframe 431. The spacers 460 are formed of a photocurable resin (a UVresin, such as an epoxy resin, in the preferred embodiment) that hardenswhen exposed to light of a wavelength within a prescribed range.

As shown in FIG. 13, the mirror clamp 470 is formed of a substantiallythree-sided clip including two engaging plate parts 471, and a linkingpart 472 linking the two engaging plate parts 471. An engaging hole 471Ais formed in each of the engaging plate parts 471. The engaging holes471A are fitted over (engaged with) engaging protrusions 431F formed onthe scanner frame 431.

The mirror clamp 470 is placed over both widthwise ends of the mirror411 so that the linking parts 472 contact a surface 411B of the mirror411 on the side opposite the reflecting surface 411A. The mirror clamp470 presses the mirror 411 toward the scanner frame 431 and fixes themirror 411 relative to the scanner frame 431.

As shown in FIG. 14B, when viewed along the longitudinal direction ofthe mirror 411, the linking parts 472 are bowed inward toward the mirror411. Vertices 472A of the linking part 472 in this bowed section contactthe mirror 411, by which contact the mirror clamp 470 applies pressureto the mirror 411.

As shown in FIG. 14A, the seating member 450 and mirror clamp 470 aredisposed such that the point at which the vertices 472A contact andapply pressure to the mirror 411 and a support point 451A at which theprotruding support part 451 contacts the mirror 411 are positioned alongan extension of the scanning path L1 for light incident on the mirror411 when projected on a plane orthogonal to the thickness direction ofthe mirror 411. Further, the vertices 472A are positioned on both sidesof the support point 451A with respect to the scanning direction of thelaser beam.

A rectangular opening 472B is formed in at least a region of the mirrorclamp 470 corresponding to the spacers 460 (the linking parts 472 in thepreferred embodiment). The opening 472B allows the light to cure thephotocurable resin (spacers 460) through the longitudinal end of themirror 411 on which the metal is not deposited.

As described above, the spacers 460 are formed of a photocurable resinin the preferred embodiment. Therefore, after adjusting the mirrors410-419 to the prescribed mounted angles, light is irradiated on thespacers 460 to set the spacers 460 for maintaining the mirrors at theadjusted angles.

Further, the mirrors 410-419 can be set to desired angles by rotating(pivoting) the mirrors about the respective protruding support parts451, thereby reliably adjusting the mirrors to appropriate angles.

Further, since the spacers 460 can be easily deformed to follow (conformto) the contact surfaces of the mirrors 410-419 prior to curing, lightcan be irradiated on the spacers 460 in this deformed state to hardenthe spacers 460. Accordingly, there is no need to consider the surfaceprecision of the spacers 460 or the mirrors 410-419.

Further, since the cured spacers 460 continue to maintain their shape(seating surface) for holding the mirrors in the prescribed angles setwhen mounting the mirrors, if the scanning unit 400 is dismantled forcleaning the mirrors 410-419, the mirrors 410-419 need only be mountedin contact with the already cured spacers 460 when reassembling thescanning unit 400. In other words, the mirrors 410-419 can be remountedon the scanner frame 431 at the appropriate mounted angles withoutreadjusting the angles after maintenance.

Therefore, the scanning unit 400 according to the preferred embodimentfacilitates reassembly (maintenance) operations and can easily maintainthe mounted angles of the mirrors 410-419 at the appropriate angle.

Further, at least the region of the mirrors 410-419 opposing the spacers460 allows light to pass for curing the photocurable resin of thespacers 460. Accordingly, the mirrors 410-419 do not impede lightirradiated onto the spacers 460, thereby avoiding such interference.

Further, the protruding support part 451 is provided on the seatingmember 450 disposed between the scanner frame 431 and the respectivemirror 410-419, and the spacers 460 disposed between the seating member450 and the respective mirror 410-419 preserve the mounted angle of therespective mirror 410-419. Therefore, the mirrors 410-419 can be fixedon the scanner frame 431 via the seating members 450.

Accordingly, if the photocurable resin (spacers 460) functions as anadhesive that bonds each of the mirrors 410-419 to the respectiveseating member 450 forming a single unit, for example, each of themirrors 410-419 and the respective seating member 450 can be treated asa single unit in which the mounted angle of the mirror 410-419 is fixed.Hence, the mirrors 410-419 can easily be removed from the scanner frame431 and remounted on the scanner frame 431 with the respective seatingmembers 450 as a unit when reassembling the scanning unit 400, withouthaving to readjust the mounted angle of the mirrors 410-419. Therefore,the scanning unit 400 according to the preferred embodiment furtherfacilitates reassembly (maintenance) operations.

Further, since photocurable resin normally bonds well with metal,forming the seating member 450 with metal, as in the preferredembodiment, reliably ensures that each of the mirrors 410-419 and therespective seating member 450 can be bonded together as a single unit.

However, the position of the seating member 450 in the longitudinaldirection of the mirror 411 is fixed by fitting the groove 453 of theseating member 450 over the protruding part 431B. Similarly, theposition of the seating member 450 in the direction orthogonal to thelongitudinal direction of the mirror 411 is fixed by restricting bothends of the seating member 450 in the extended direction of the groove453 with the step parts 431C formed on the protruding part 431B.

However, it is not possible to prevent the seating member 450 fromcoming off the scanner frame 431 simply by inserting the protruding part431B into the groove 453. Further, since the spacers 460 are formed of aphotocurable resin, although the photocurable resin can be expected tofunction as an adhesive for bonding the seating member 450 to the mirror411, it is unlikely that the mirror 411 and seating member 450 will befirmly fixed together as a single unit with only the spacers 460.

Therefore, the mirror clamps 470 press the mirrors 410-419 toward thescanner frame 431, reliably fixing the units configured of the mirrors410-419 and their respective seating members 450 on the scanner frame431.

Further, the opening 472B through which light can be transmitted forhardening the photocurable resin is provided in at least the region ofthe mirror clamps 470 corresponding to the spacers 460. Therefore, notonly can the units configured of the mirrors 410-419 and theirrespective seating members 450 be fixed to the scanner frame 431reliably, but also this configuration prevents the mirror clamps 470from interfering with light irradiated onto the spacers 460.

Displacement of the light beam relative to variations in the mountedangle of the mirrors 410-419 increases in regions farther away from therotating (pivoting) support points of the mirrors. If the light beam isincident on a region of the mirrors 410-419 away from the rotatingsupport point thereof, adjustments in the mounted angles of the mirrors410-419 would greatly change the length of the optical path.

However, since the protruding support parts 451 contact the reflectingsurfaces 411A of the mirrors 410-419 in an area positioned along anextension of the scanning path L1 of the laser beam in the preferredembodiment, the mounted angles of the mirrors 410-419 are adjusted byrotating (pivoting) the mirrors 410-419 about a region positioned on theextension of the scanning path L1. Therefore, the present inventionprevents large changes in the length of the optical path when adjustingthe mounted angle of the mirrors 410-419.

Further, the vertices 472A at which the mirror clamps 470 contact andapply pressure to the mirrors 410-419 and the support points 451A atwhich the protruding support parts 451 contact the mirrors 410-419 arealigned in a direction parallel to the scanning path L1 when the pointsare projected onto a plane orthogonal to the thickness direction of themirrors 410-419. Accordingly, the vector of force applied to thevertices 472A and the vector of reaction force generated at the supportpoint 451A cancel each other so that a moment for twisting the mirrors410-419 is not generated in the same.

Since it is possible to prevent twisting deformation in the mirrors410-419, the light beam can be guided to the photosensitive drums 510reliably.

Further, since the vertices 472A of the linking parts 472 contact andapply pressure to the mirrors 410-419 on either side of the supportpoints 451A contacting the mirrors 410-419 in a direction parallel tothe scanning direction of the laser beam, the pressing force of themirror clamps 470 can be applied uniformly (symmetrically) about thesupport point at which the protruding support parts 451 contact themirrors 410-419. Therefore, this construction can prevent the pressureapplied by the mirror clamps 470 from bending or deforming the mirrors410-419 unevenly, thereby reliably guiding light beams to thephotosensitive drums 510.

As shown in FIG. 3, the scanning unit 400 in a color laser printer 100has mirrors 410-419 of a number at least equal to the number ofphotosensitive drums 510. If the mounted angles of the mirrors 410-419are inexact, the paths of light beams irradiated onto the photosensitivedrums 510 are not parallel to the photosensitive drums 510, but ratherslanted or curved, making it impossible to guide the laser beams toprescribed positions on the photosensitive drums 510. As a result, thequality of images formed on the paper suffers.

A color laser printer 100 forms color images by transferring tonerimages carried on photosensitive drums 510 provided for each of thecolors cyan, magenta, yellow, and black, superimposing the toner imageson paper. Hence, if the laser beams irradiated onto the photosensitivedrums 510 follow slanted or curved trajectories, the superimposed imagesin each color will not be properly registered, resulting in a remarkabledecline in image quality.

In other words, with a color laser printer 100 it is more important toadjust and maintain the mounted angles of the mirrors 410-419 with highprecision than with a single-color laser printer. Since the mountedangles of the mirrors 410-419 can be adjusted and maintained with highprecision when using the scanning unit 400 according to the preferredembodiment, the color laser printer 100 using the scanning unit 400 canform high quality color images.

In the tandem color laser printer 100 shown in FIG. 3, a plurality ofthe photosensitive drums 510 are arranged in series along thepaper-conveying direction, and laser beams are irradiated from aplurality of locations toward each of the photosensitive drums 510.Since each of the laser beams must be focused on the respectivephotosensitive drum 510 with great accuracy, it is particularlyeffective to use the scanning unit 400 according to the preferredembodiment in this laser printer 100 in order to adjust and maintain themounted angles of the mirrors 410-419 with accuracy.

Second Embodiment

In the laser printer 100 according to a second embodiment shown in FIG.15, a cleaning pad 561 is provided on the casing 560 of the processcartridge 500 for cleaning the exit hole covers 436. Accordingly, whenpulling the casing 560 out of the laser printer 100 to replace theprocess cartridges 500, for example, the cleaning pad 561 provided onthe casing 560 cleans the four exit hole covers 436 while movingtogether with the casing 560, as shown in FIG. 16.

Hence, in the preferred embodiment, the exit hole covers 436 can besimultaneously cleaned when moving the casing 560 to remove or insertthe process cartridges 500, thereby facilitating cleaning of the exithole covers 436.

Third Embodiment

In the preferred embodiments described above, the protruding supportpart 451 formed on the seating member 450 contacts the reflectingsurface 411A of the mirror 411 at substantially the widthwise center ofthe mirror (the center point in a direction orthogonal to thelongitudinal direction and thickness direction), that is, along anextension of the scanning path L1. However, in the third embodimentshown in FIG. 17, the protruding support part 451 is positioned tocontact the reflecting surface 411A of the mirror near one widthwise endthereof, while a single spacer 460 is disposed on the other widthwiseend.

Fourth Embodiment

In the embodiments described above, the mirror clamp 470 is formed of ametal, and an opening 472B is formed in the mirror clamp 470 forallowing the passage of light used to cure the spacers 460. However, inthe fourth embodiment shown in FIGS. 18A and 18B, at least the linkingparts 472 of the mirror clamp 470 are formed of a transparent material(such as a polycarbonate or other resin), thereby eliminating theopening 472B.

Variations of the Embodiments

While the invention has been described in detail with reference to thespecific embodiment thereof, it would be apparent to those skilled inthe art that various changes and modifications may be made thereinwithout departing from the spirit of the invention.

For example, in the preferred embodiments described above, the opticalscanner according to the present invention is applied to a scanning unit400 in a tandem color laser printer. However, the present invention isnot limited to this configuration, but may be applied to a scanning unit400 for a single-color laser printer, for example.

Further, the protruding support part 451 is provided on the seatingmember 450 in the preferred embodiments described above, but the presentinvention is not limited to this configuration. For example, theprotruding support part 451 may be provided directly on the scannerframe 431, eliminating the seating member 450. However, if the mirrors410-419 were to be directly mounted on the scanner frame 431 withoutusing the seating member 450 and the mirrors 410-419 were to be mountedon the scanner frame 431 with a photocurable resin (the spacers 460),then it may be impossible to remove the mirrors 410-419 from the scannerframe 431 when disassembling the scanning unit 400 for maintenance.

Further, the spacer 460 functions as an adhesive to bond the mirrors410-419 to their respective seating members 450 in the preferredembodiments described above, but the present invention is not limited tothis construction. The spacer 460 may function simply to maintain themounted angles of the mirrors 410-419.

Further, metal was not deposited through vapor deposition in the regionof the mirrors 410-419 corresponding to the spacers 460 so that thisregion can transmit light, but the present invention is not limited tothis construction. For example, an opening may be provided in theregions of the mirrors 410-419 corresponding to the spacers 460 to allowthe transmission of light.

Further, since light is irradiated from the side of the mirrors 410-419opposite the spacers 460, light can pass through the region of themirrors 410-419 corresponding to the spacers 460, but the presentinvention is not limited to this construction. For example, light may beirradiated onto the spacers 460 laterally.

Further, the seating member 450 is formed of a metal in the preferredembodiments described above, but may also be formed of a syntheticresin, for example.

Further, the mirror clamps 470 press the mirrors 410-419 toward thescanner frame 431 and fix the mirrors 410-419 on the scanner frame 431,but the present invention is not limited to this construction. Forexample, the mirrors 410-419 may be fixed to the scanner frame 431simply by the adhesive function of the spacers 460, thereby eliminatingthe mirror clamp 470.

Further, the opening 472B is provided in order to irradiate light on thespacers 460 in the preferred embodiments described above, but thepresent invention is not limited to this construction. The mirror clamps470 may instead by offset from the spacers 460, eliminating the opening472B.

Further, the protruding support part 451 contacts the reflecting surface411A of the mirror 411 at a position on an extension of the scanningpath L1 in the preferred embodiments described above, but the presentinvention is not limited to this construction.

Further, in the preferred embodiments described above, the contact point(support point) between the protruding support part 451 and reflectingsurface 411A and the pressure application point of the mirror clamp 470on the mirror 411 when projected onto a plane orthogonal to thethickness direction of the mirrors 410-419 are aligned in the scanningdirection, but the present invention is not limited to thisconstruction.

Further, the cover clamp 440 presses against and fixes both the exithole cover 436 and the cover member 432 against the scanner frame 431 inthe preferred embodiments described above, but the present invention isnot limited to this construction. For example, the cover member 432 maybe detachably assembled to the scanner frame 431 with a fixing means,such as screws, while the exit hole cover 436 may be pressed against andfixed to the cover member 432 or scanner frame 431 or may be fixed tothe cover member 432 with a bonding means, such as an adhesive.

Further, in the preferred embodiments described above, the cover clamp440 presses and fixes the exit hole cover 436 to the casing 430 (covermember 432) side on both ends of the exit hole cover 436 in the scanningdirection (longitudinal direction), but the present invention is notlimited to this construction. For example, the cover clamp 440 may beconfigured to press the exit hole cover 436 against the casing 430(cover member 432) along the entire outer edges of the exit hole cover436.

Further, in the preferred embodiments described above, the cover clamp440 is substantially L-shaped, but the present invention is not limitedto this construction.

Further, the surface of the exit hole cover 436 on the photosensitivedrum 510 side in the preferred embodiments is positioned closer to thephotosensitive drums 510 than the outer surface 430A of the casing 430,but the present invention is not limited to this construction. Forexample, the surface of the exit hole cover 436 on the photosensitivedrum 510 side may be positioned flush with the outer surface 430A or maybe positioned closer to the toric lens 420 side than the outer surface430A.

In the preferred embodiments described above, the cover member 432 isprovided separately from the main casing part (scanner frame 431 andscanner cover 433), but the present invention is not limited to thisconstruction. For example, the cover member 432 may be formed integrallywith the scanner frame 431.

In the preferred embodiments described above, the cover member 432 isformed of a metal, but may be formed of synthetic resin or the likeinstead. Further, the electric harness 406A is disposed in a regioncorresponding to the metal cover member 432 in the preferred embodimentsdescribed above, but the present invention is not limited to thisconstruction.

In the preferred embodiments described above, the cover member 432 ismanufactured by a pressing method, but the present invention is notlimited to this construction.

Further, in the preferred embodiments described above, a portion of thetoric lenses 420 disposed as the last optical member along the opticalpath is positioned inside the exit hole 435, but the present inventionis not limited to this construction.

Further, in the preferred embodiments described above, a plurality ofexit holes 435 are formed in the cover member 432, but a cover member432 may be provided for each of the exit holes 435.

In the preferred embodiments described above, the surfaces of theplurality of exit hole covers 436 on the photosensitive drum 510 sideare all positioned substantially along the same plane, but the presentinvention is not limited to this construction.

Further, in the preferred embodiments described above, the exit holecover 436 is provided on the outside of the casing 430, but the exithole cover 436 may be provided on the inside of the casing 430 instead.

1. An optical scanner comprising: a frame having a frame surface and afirst portion; a light source configured to emit a light beam; anoptical member mounted on the frame to guide the light beam to ascanning target, the optical member having a first surface opposing theframe surface and a second surface opposing the first surface; a seatingmember disposed between the frame surface and the first surface, andhaving a seating surface opposing the first surface and a second portionremovably fit with the first portion; and a spacer configured tomaintain the optical member at a predetermined position with respect tothe frame, the spacer being formed of a photocurable resin that is curedin response to a predetermined light having a wavelength within aprescribed range, the spacer being disposed between the seating surfaceand the first surface, the optical member being coupled with seatingmember by the cured spacer.
 2. The optical scanner according to claim 1,wherein the optical member has a light transmitting part configured totransmit the predetermined light, the spacer being disposed between thefirst portion and the first surface of the transmitting part.
 3. Theoptical scanner according to claim 1, further comprising a support partdisposed between the seating surface and the first surface and extendingin a predetermined direction parallel to the seating surface, the spacerbeing disposed on at least one side of the support part.
 4. The opticalscanner according to claim 3, wherein a space is formed between theframe surface and the first surface, the support part dividing the spaceinto a first space and a second space, the spacer being disposed on bothof the first space and the second space respectively.
 5. The opticalscanner according to claim 3, wherein the support part is disposed onthe seating member.
 6. The optical scanner according to claim 5, whereinthe spacer is bonded to the seating member.
 7. The optical scanneraccording to claim 5, wherein the seating member is formed of a metaland the frame is formed of a resin.
 8. The optical scanner according toclaim 3, further comprising a pressing member configured to press theoptical member toward the frame.
 9. The optical scanner according toclaim 8, wherein the pressing member has a covering part partiallycovering the second surface of the optical member, wherein the coveringpart is formed with an opening through which the predetermined lighttransmits.
 10. The optical scanner according to claim 9, furthercomprising a scanning member configured to change a direction in whichthe light beam is transmitted so that the light beam scans on thescanning target along a scanning path, wherein the predetermineddirection aligns with the scanning path when viewed in a directionorthogonal to the first surface of the optical member.
 11. The opticalscanner according to claim 10, wherein the pressing member has acontacting part extending in the predetermined direction and contactingthe second surface of the optical member, the contacting part aligningwith the support part when viewed in a direction orthogonal to the firstsurface of the optical member.
 12. The optical scanner according toclaim 11, wherein the pressing member has a first connecting partextending from the contacting part in a first direction orthogonal tothe predetermined direction, a second connecting part extending from thecontacting part in a second direction opposing the first direction, afirst engaging part connected to the first connecting part and engagingthe frame, and a second engaging part connected to the second connectingpart and engaging the frame.
 13. The optical scanner according to claim1, wherein the optical member comprises a mirror.
 14. An image-formingdevice comprising: a plurality of image-carrying members on which aplurality of light beams is scanned, respectively, to form a color imageon a recording medium; and an optical scanner including: a frame havinga frame surface and a first portion; a light source configured to emitthe plurality of light beams; a plurality of optical members mounted onthe frame to guide the plurality of light beams to the plurality ofimage-carrying members, each optical member having a first surfaceopposing the frame surface and a second surface opposing the firstsurface; a seating member disposed between the frame surface and eachfirst surface, and having a seating surface opposing each first surfaceand a second portion removably fit with the first portion; and aplurality of spacers configured to maintain each optical member at apredetermined position with respect to the frame, each spacer beingformed of a photocurable resin that is cured in response to apredetermined light having a wavelength within a prescribed range, eachspacer being disposed between the seating surface and each firstsurface, each optical member being coupled with seating member by thecured spacer; wherein a number of the plurality of optical members is noless than a number of the plurality of image-carrying members.